Diversity reception schemes, wherein a transmitted signal is essentially simultaneously received on two or more antennas of a receiver system, are known. An advantage of a diversity system is that, as a result of a multitude of factors, one of the antennas may provide the receiving system with a signal superior to the signals received at the other antennas of the system. For example, the signals received on each antenna may be received with different amounts of disturbances (such as noise, distortion, multi-path interference, jamming, etc.).
When a transmitted signal is received on multiple antennas, it is possible in decoding to exploit the differences in the signals received by those antennas. In prior systems, the signals received by the multiple antennas are analyzed, determinations are made, and a single signal is output to a digital decoder as a single stream of soft decisions. The diversity determination component may simply select one of the multiple received signals to output to the decoder or it may combine the multiple signals in some way to create the output signal.
Typical diversity combining schemes, however, only process the received signal on a symbol-by-symbol basis. Since only a single stream of information is output to the decoder, much of the received data and associated coding received via the multiple inputs is not passed to the decoder and therefore cannot be used to help decode the received signal. As a result, such systems do not exploit the redundancies that occur within the error correction and detection coding that may be transmitted with the received data.
In addition, error correction coding schemes have been developed to increase the reliability and efficiency of radio frequency communications. For example, a class of codes known by many as low density parity check codes has been developed for this purpose. Codes popularly known as Turbo Codes provide a specific example of such a coding scheme. Such codes can be decoded at the receive end by a process known as iterative decoding. U.S. Pat. No. 5,406,570, issued Apr. 11, 1995, and U.S. Pat. No. 5,446,747, issued Aug. 29, 1995, provide examples and descriptions of prior encode and decode systems using error protection coding and iterative decoding.
Presently, there exists a need for a multiple input diversity decoding system that can exploit, rather than discard, the redundancies in received low density parity check source coding. Further needed is a multiple input diversity decoding system that is practical for use with a wide variety of communication systems and coding schemes. In addition, a multiple input diversity decoding system that can be used with various types of input signals, wired and wireless, radio frequency and non-radio frequency, is needed.